meta viewport: can not use “width=640” with “initial-scale=1.0”?

Question

when I set viewport with

<meta name="viewport" content="width=640">

I can create a square div takes half of the screen by following css

.sq {
  width: 320px;
  height: 320px;
  background-color: coral;
}

but I after I modify it to

<meta name="viewport" content="width=640, initial-scale=1.0">

it seems broken, the square with 320px width takes more than half of the screen.

what does "initial-scale=1.0" do here, can anyone tell me the details ?

Answer 1

以px为单位

<meta name="viewport" content:"width=640px">